How old is it?

If it's less than ten years old then you'll need to SVA it then register it with a V55, SVA cert, insurance cert & proof of age.

If it's more than ten years then you don't need the SVA but will need an MOT instead.

I've been out the bike trade for about 5 years tho so that's assuming nothing has changed since.

Registration fee was £25 back then plus you'll need to tax it.